Epileptic Encephalopathy in Childhood: A Stepwise Approach for Identification of Underlying Genetic Causes.

Epilepsy is one of the most common neurological disorders in childhood. Epilepsy associated with global developmental delay and cognitive dysfunction is defined as epileptic encephalopathy. Certain inherited metabolic disorders presenting with epileptic encephalopathy can be treated with disease specific diet, vitamin, amino acid or cofactor supplementations. In those disorders, disease specific therapy is successful to achieve good seizure control and improve long-term neurodevelopmental outcome. For this reason, intractable epilepsy with global developmental delay or history of developmental regression warrants detailed metabolic investigations for the possibility of an underlying treatable inherited metabolic disorder, which should be undertaken as first line investigations. An underlying genetic etiology in epileptic encephalopathy has been supported by recent studies such as array comparative genomic hybridization, targeted next generation sequencing panels, whole exome and whole genome sequencing. These studies report a diagnostic yield up to 70%, depending on the applied genetic testing as well as number of patients enrolled. In patients with epileptic encephalopathy, a stepwise approach for diagnostic work-up will help to diagnose treatable inherited metabolic disorders quickly. Application of detailed genetic investigations such as targeted next generation sequencing as second line and whole exome sequencing as third line testing will diagnose underlying genetic disease which will help for genetic counseling as well as guide for prenatal diagnosis. Knowledge of underlying genetic cause will provide novel insights into the pathogenesis of epileptic encephalopathy and pave the ground towards the development of targeted neuroprotective treatment strategies to improve the health outcome of children with epileptic encephalopathy.